1. Field of the Invention
This invention relates to a process for making poly-p-phenylene terephthalamide by a solution polymerization wherein the solvent system comprises an N-alkyl-substituted amide and a quaternary ammonium chloride compound.
2. Description of the Prior Art
Solution polymerization of aromatic diamines with aromatic diacid halides is well known. For example, U.S. Pat. No. 3,063,966 discloses a solution polymerization to yield such aromatic polyamides wherein the solvent medium has, as its primary constituent, an "amide-type" organic compound. Examples of the "amide-type" organic compounds are dimethyl acetamide, tetramethyl urea, N-acetyl pyrrolidone, N-methyl pyrrolidone, and hexamethyl phosphoramide.
U.S. Pat. No. 4,169,982 discloses a solution polymerization to yield poly-p-phenylene terephthalamide and copolymers by use of a solvent medium which can include N-alkyl-substituded amides and salts of alkali or alkaline earth metals. Specific examples of N-alkyl-substituted amides include dimethyl acetamide, N-methyl pyrrolidone, diethyl acetamide, and tetramethyl urea. Specific examples of metal salts include LiCl and CaCl.sub.2, among many others.
U.S. Pat. No. 4,308,374 discloses a solution polymerization to yield poly-p-phenylene terephthalamide by use of a solvent system made from N-methyl pyrrolidone and CaCl.sub.2 wherein the CaCl.sub.2 is present in an amount which is at least 5 percent, by weight, of the weight of the N-methyl pyrrolidone.